1. Field of the Invention
The present invention relates to an apparatus for printing on continuous paper having a function for stacking the continuous paper after it is printed, and to a device for stacking the paper. More particularly, the invention relates to an apparatus that is suited for moving paper at high speed.
2. Description of the Related Art
An ordinary continuous paper has a perforation after each page and is folded at a mountain perforation and at a valley perforation. The paper carried by a tractor from a printer unit is folded along the perforation in a zig-zag manner by a paper-folding mechanism and is stacked on a paper table.
Here, a predetermined positional relationship must be maintained at all times between the uppermost position of the paper that is stacked and the folding mechanism in order to correctly stack the paper on the table maintaining a folding precision at the perforations of the paper relative to the folding mechanism.
So far, the uppermost position of the stacked paper has been detected and has been so controlled that the uppermost portion of the paper that is stacked lies within a specified range at all times. That is, according to the prior art, after the start of printing, an interval is set for periodically lowering the paper table. After the interval has elapsed, the paper table is greatly lowered and is, then, gradually raised. In the step of raising the paper table, it is checked whether there is paper at the uppermost portion. When paper is detected, the paper table is halted. When no paper is detected, the paper table continues to rise. According to the conventional control operation as described above, the operation is repeated in that the paper table is greatly lowered at regular time intervals and is, then, raised until the upper end of the paper arrives at the sensor position.
When the paper-folding mechanism swings right and left to fold the paper along the perforation, however, the paper just before being stacked shades the sensor that detects the uppermost portion of the paper depending upon the swinging angle, and the sensor often incorrectly detects paper though it really does not exist. The sensor for detecting the uppermost portion of the paper is constituted by an opposing pair of light-emitting element and light-receiving element, and the presence of the paper is detected by relying upon the interruption of light. Therefore, when the paper, just before being folded, temporarily interrupts light to the light-receiving element due to the angle of the paper-folding mechanism, the sensor judges that the paper exists. In this case, therefore, the paper table comes into a halt.
Thus, the position of the paper-folding mechanism that swings temporarily causes the sensor to lose stability due to interruption of light to the sensor by the paper, just before being folded, hindering the detection of the uppermost portion of the really stacked paper while permitting, in other moments, the sensor to accomplish the normal detection. These two states periodically occur while the paper-folding mechanism is swinging.
In the state where the sensor that detects the uppermost portion of the paper is producing an unstable output, it happens that the paper table is regarded to have pushed the uppermost portion of the paper to a predetermined height if the sensor that detects the uppermost portion malfunctions even though the paper table is really at a low position separated away from the paper-folding mechanism.
Therefore, when the sensor that detects the uppermost portion of the paper produces an unstable output while the paper table is being raised, the operation for raising the paper table is discontinued though the paper table is not really pushing up the uppermost portion of the paper to a predetermined height. Then, when the paper-folding mechanism moves in excess of a state where the sensor produces an unstable output, the sensor normally detects the presence of no paper. Accordingly, the operation for raising the table is resumed. According to the conventional control operation, therefore, the paper table finally arrives at the predetermined height after having repeated the raising and stopping several times.
The operation for repetitively raising and stopping of the paper table exerts a burden on the motor for raising and lowering the table. Besides, the behavior of when the paper table is brought into a halt adversely affects the operation for precisely raising or lowering the paper table so that the uppermost portion of the paper lies within a predetermined range.
So far, despite the paper table being intermittently raised or lowered as described above, the speed for carrying the paper is not so high and the performance of the electric motor for raising or lowering the table follows the rate for stacking the papers on the table. Therefore, the height of the paper table could be controlled to meet the practical use.
According to another prior art, provision is made of plural sensors for detecting the uppermost surface of the paper, and the rise of the table is halted when the uppermost portion is detected by all of the sensors. This makes it possible to conduct the control operation by taking into consideration the case where the upper surface of the stacked paper is irregular.
In raising the paper table up to a specified position, too many times of repetition of stopping and raising, as in the conventional operation for raising and lowering the paper table, exerts a burden on the motor for raising and lowering the paper table, requires additional electric power for driving the motor and shortens the life of the motor.
Besides, it is a tendency to carry the papers at sharply increasing speeds to meet the modern demand for executing the printing processing at high speed. At present, a paper of 11 inches is discharged and stacked in an amount of 5 to 6 pieces a second reckoned as an A4-size. In the future, it is expected that the paper will be discharged in further increased amounts, and the paper-folding mechanism swings at a correspondingly increased speed. Therefore, if the sensor that detects the uppermost portion of the paper periodically produces outputs in a normal state and in an unstable state, the stopping and raising of the paper table are repeated at high speeds and an increased burden is exerted on the motor for raising and lowering the paper table. Further, upon receiving a burden, the motor becomes no longer capable of operating as instructed. Due to the repetition of the movement of the paper table, further, the paper may often not be stacked to a specified amount.
As means for solution, it can be contrived to use a motor of high performance that withstands high-speed operation for driving the table and to increase the raising/lowering speed. This, however, causes a great increase in the cost of the table drive mechanism. Further, if the speed of the table is simply increased, the motor overruns at the time when the paper table is brought into a halt resulting in a decrease in the precision in the height of the paper table.
In recent years, further, printing has been executed in a variety of modes, such as printing a paper on which a thick medium like a card has been stacked and printing a dense image on half of the paper. Due to the kind of the paper or due to deviated printing, therefore, the uppermost surface of the paper stacked on the table often becomes inclined in the right-and-left direction.
When the paper is to be stacked in this state, means for detecting the uppermost portion provided in a number of only one detects the paper. When the paper table is brought into a halt, a high portion of the uppermost surface of the paper that is inclined may already be higher than the specified position causing inconvenience such as defective stacking, damage to the paper, etc.
According to the above conventional control method having plural sensors for detecting the uppermost portion and in which the rise of the table is halted when the uppermost surface is detected by all of the sensors, an irregular surface of the stacked paper can be brought into consideration, which, however, is not fully effective in detecting the papers that are stacked in a deviated manner.
It is therefore an object of the present invention to provide an apparatus for printing continuous paper and a device for stacking the paper capable of stacking the papers maintaining good precision without exerting a burden on the motor for raising and lowering, by simply using a conventional motor mechanical portion for raising and lowering and, hence, without greatly driving up the cost, featuring a simple constitution and lending itself well to high-speed processing.
Another object of the present invention is to provide an apparatus for printing continuous paper at high speed and a device, for stacking the paper, capable of smoothly raising and lowering the paper table irrespective of the position of the paper-folding mechanism as a result of not using the unstable output of the sensor that detects the uppermost portion of the paper.
In order to accomplish the above-mentioned objects, the present invention deals with an apparatus for printing a continuous paper comprising:
a printer unit for printing a continuous paper;
a paper table on which the continuous paper carried through the printer unit is folded and stacked;
an uppermost portion sensor for detecting the uppermost position of the paper stacked on the paper table;
a guide mechanism for guiding the continuous paper to the paper table;
a moving mechanism for changing the distance between the paper table and the guide mechanism; and
a control circuit for controlling the moving mechanism based on the output of the uppermost portion sensor to change the distance between the paper table and the guide mechanism;
wherein, when the uppermost portion sensor is producing an unstable output due to the paper being stacked, the control circuit so works that the moving mechanism continues its operation even when the uppermost portion sensor has detected the paper.
Even when the sensor is producing an unstable output as in a state where the paper being stacked is shading the sensor, therefore, such an unstable output is not used and, hence, a wasteful operation is not effected. Accordingly, the distance between the paper guide mechanism and the paper table can be changed without exerting an excess load on the moving mechanism such as the motor for raising and lowering the paper table, and the paper can be stacked on the paper table to meet the high-speed processing.
The invention further deals with an apparatus for printing a continuous paper comprising:
a printer unit for printing a continuous paper;
a paper-folding mechanism for successively folding the continuous paper carried through the printer unit;
a paper table for stacking the folded paper;
a table-moving mechanism for moving the paper table up and down;
an uppermost portion sensor for detecting the uppermost position of the paper stacked on the paper table; and
a control circuit for controlling the rising/lowering motion of the paper table based on the output of the uppermost portion sensor;
wherein, when the uppermost portion sensor is producing an unstable output due to the paper as before being stacked, the paper table continues to operate even when the uppermost portion sensor has detected the paper.
Even when the sensor is producing an unstable output as in a state where the paper being stacked is shading the sensor, therefore, the paper table continues to operate. Accordingly, the distance between the uppermost position of the stacked paper and the paper-folding mechanism is maintained constant without exerting a load on the drive motor of the paper table-moving mechanism, and the paper can be stacked during high-speed processing.
The invention further deals with an apparatus for printing continuous paper comprising:
a printer unit for printing continuous paper;
a paper-folding mechanism for successively folding the continuous paper carried through the printer unit;
a paper table for stacking the folded paper;
a table-moving mechanism for moving the paper table up and down;
an uppermost portion sensor for detecting the uppermost position of the paper stacked on the paper table; and
a latch signal-holding circuit for holding the output of the sensor;
wherein, when the uppermost portion sensor is producing an unstable output due to the position of the paper-folding mechanism, a latch signal is formed so that the latch signal-holding circuit will not change its output, and the rising/lowering motion of the paper table is controlled by the latch signal.
Even when the uppermost portion sensor is producing an unstable output, as in a state where the sensor is shaded by the paper due to the position of the paper-folding mechanism, the value detected the previous time is held as a latch signal. The uppermost portion of the paper is detected by regarding the latch signal to be the output of the uppermost portion sensor enabling the paper table to be raised and lowered. There is thus provided an apparatus that allows high-speed processing.
The invention according to a further aspect deals with an apparatus for printing continuous paper comprising:
a printer unit for printing continuous paper;
a paper-folding mechanism for successively folding the continuous paper carried through the printer unit;
a paper table for stacking the folded paper;
a moving mechanism for moving the paper table up and down;
plural uppermost portion sensors provided at different positions facing the paper-folding mechanism for detecting the uppermost position of the paper stacked on the paper table; and
plural latch signal-holding circuits for holding the outputs of the plural uppermost portion sensors;
wherein, when the uppermost portion sensors are producing unstable outputs due to the position of the paper-folding mechanism, latch signals are formed so that the latch signal-holding circuits will not change their outputs, and the movement of the paper table is controlled when one or more of the plural latch signals have detected the uppermost portion of the paper.
By avoiding the state where the uppermost portion sensors produce unstable outputs, it is possible to detect the uppermost portion of the paper in a more reliable state and, hence, to control the rising/lowering motion of the paper table while maintaining good precision.
Further, even when the papers are stacked in a deviated manner, the paper-folding mechanism and the uppermost position of the paper can be so controlled as to lie within a specified range at all times.